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Pancreatic A and B cell hyperfunction in the Mendenhall syndrome
Diabetologia
|July 1, 1983
Summary
This study examines a teenager with severe insulin resistance and acanthosis nigricans, finding a receptor defect and B cell hypersecretion. High exogenous insulin levels were confirmed, indicating the body
Area of Science:
- Endocrinology
- Metabolic Disorders
- Molecular Biology
Background:
- Investigating severe insulin resistance in adolescents presenting with acanthosis nigricans.
- Understanding the role of insulin receptors and endogenous insulin secretion in complex metabolic conditions.
Observation:
- A 16-year-old male exhibited persistent hyperglycemia (16 mmol/l fasting) and acanthosis nigricans, indicative of significant insulin resistance.
- Markedly decreased insulin receptor number and affinity were observed, alongside extremely high levels of immunoreactive insulin (1344–2400 mU/l).
- Elevated endogenous C-peptide (2.2–3.5 pmol/ml) and proinsulin (approx. 1 pmol/ml) levels suggested B cell hypersecretion.
Findings:
- Analysis revealed a low C-peptide to immunoreactive insulin molar ratio (approx. 0.3), confirming predominantly exogenous insulin administration.
- A high proinsulin to C-peptide molar ratio (0.23–0.45) indicated impaired proinsulin conversion, potentially due to chronic B cell overstimulation.
- Immunoreactive glucagon levels were normal fasting but elevated post-arginine infusion.
Implications:
- The findings suggest a severe insulin receptor defect as the primary cause of insulin resistance in this case.
- Chronic B cell hyperstimulation may lead to functional impairment, characterized by increased proinsulin secretion.
- This case highlights the complex interplay between receptor defects, exogenous insulin use, and endogenous pancreatic beta-cell function in severe insulin resistance syndromes.